A plurality of integrated circuits is typically fabricated relative to a semiconductor wafer or other semiconductor substrate. The substrate is subjected to various treating steps, such as material growth, deposition, etching, ion implantation, etc., in forming the integrated circuitry. Accordingly, the semiconductor substrate is subjected to a plurality of different treatments prior to completion. Recently, the semiconductor substrates being processed have become increasingly thinner and fragile leading to different techniques for supporting the individual substrates through the various different treatments to which they are subjected.
One manner of supporting such substrates is to adhere individual substrates to a rigid carrier with a temporary adhesive. At the conclusion of all processing, the semiconductor substrate is removed from the rigid carrier which can then be used again to process another semiconductor substrate. Use of such rigid carriers is not, however, without drawbacks. For example, considerable time is spent in preparing the carrier for the adhesive bonding, the actual bonding process itself, and in the de-bonding which also includes cleaning processes with expensive solvents. Further, the temporary adhesives can have poor high temperature stability, and tend to outgas material which can adversely effect the treating of the semiconductor substrate.
Another manner of retaining semiconductor substrates for processing uses electrostatic carriers. Such enable reversible bonding of semiconductor substrates by electrostatic attraction forces which are induced by a near-permanent polarization state of one or more dielectric layers. With electrostatic carriers, a semiconductor substrate is received against a dielectric side of a carrier substrate. The semiconductor substrate is typically provided at a ground potential, and suitable positive voltage is applied to a conductive electrode on the electrostatic carrier to provide a positive/negative electrostatic attraction force at an interface of the semiconductor substrate and electrostatic carrier. The attraction force remains after removal of the external voltage sources, thereby enabling the semiconductor substrate to be treated with various different processing steps. At the conclusion of the various treatments, the electrostatic attraction force can be removed by shorting the electrostatic carrier electrode and semiconductor substrate relative to one another, or by applying a suitable negative voltage to the electrostatic carrier electrode.
Accordingly, the time for bonding and de-bonding is very short in comparison to use of temporary adhesives. Further, electrostatic bonding enables subsequent processing of the semiconductor substrates at very high temperatures without the effects of outgassing, blistering, etc. Further, cleaning of the semiconductor substrate upon de-bonding that is required after de-bond using temporary adhesive technology can be eliminated.
However, commercially available electrostatic carriers are not practically capable of wet immersion processing, for example electroplating, wet etching, and wafer cleaning where the carrier with substrate bonded thereto is typically immersed in an aqueous liquid. This is because an electric path can be created within the liquid from the electrostatic carrier substrate electrode to the semiconductor substrate, thereby removing the electrostatic attraction force and de-bonding the semiconductor substrate from the electrostatic carrier.